1. Field of Invention
The present invention relates to an electronic watch such as a wristwatch, a stopwatch and the like, for counting and presenting time.
2. Description of Related Art
Electronic watches that employ a flat display such as a liquid crystal display to present numeric information and the like thereon are well known. For example, an electronic watch employing a liquid crystal display comprises a pair of polarizers 52 and 53 with a liquid crystal element 51 interposed therebetween, and a light emitting element 54 arranged on the underside of the polarizer 53 as shown in FIG. 21. The pair of polarizers 52 and 53 are arranged such that their polarization axes are mutually perpendicular.
In such a conventional electronic watch, the ambient light is used to present numeric information and the like when there is light (daytime) and the light emitting element 54 emits light as necessary to present numeric information and the like when there is not light (nighttime). To present numeric information, a predetermined ON voltage is applied between electrodes of the liquid crystal element 51, and an area where no voltage is applied or where an OFF voltage is applied is a background of white or any other appropriate color. As shown, the area where the ON voltage is applied to present information is represented by "ON" and the area where no voltage or the OFF voltage is applied is represented by "OFF."
When the ambient light is used to present the background (namely with the liquid crystal element 51 at an OFF state), light linearly polarized in a direction parallel to the page of FIG. 21, out of the ambient light, namely the natural light, is transmitted through the polarizer 52 as represented by an arrow P, and is twisted by 90.degree. in polarization direction by the liquid crystal element 51 at an OFF state, thereby becoming light linearly polarized in a direction perpendicular to the page of FIG. 21. The linearly polarized light is then transmitted through the polarizer 53, and is scattered on the surface of the light emitting element 54, and part of the scattered light is transmitted through the polarizer 53, liquid crystal element 51 and polarizer 52 in that order, and is presented outside, and the background is thus recognized as a white background.
When the ambient light is used to present numeric information and the like (namely with the liquid crystal element 51 at an ON state), light linearly polarized in a direction parallel to the page of FIG. 21, out of the ambient light, is picked out by the polarizer 52, and is transmitted through the liquid crystal element 51 as represented by an arrow Q. Since the liquid crystal element 51 is at an ON state, the linearly polarized light ray keeps its polarization direction parallel to the page of FIG. 21 without being twisted, and is thus absorbed by the polarizer 53. As a result, this area is externally recognized as "black."
In this way, numbers and the like in black, indicating time and other information, are presented on the white background when the ambient light is used for presentation.
On the other hand, when the emission of the light emitting element 54 is used to present the background (namely with the liquid crystal element 51 at an OFF state), as represented by an arrow C, light linearly polarized in a direction perpendicular to the page of FIG. 21, out of the emission of the light emitting element 54, namely the natural light, is picked out by the polarizer 53, and is twisted by 90.degree. in polarization direction by the liquid crystal element 51 at an OFF state, thereby becoming light linearly polarized in a direction parallel to the page of FIG. 21, and is transmitted through the polarizer 52 to be recognized externally. The color of the light recognized is the emission color of the light emitting element 54, and is typically white.
When the emission of the light emitting element 54 is used to present numeric information and the like (namely with the liquid crystal element 51 at an ON state), as represented by an arrow D, light linearly polarized in a direction perpendicular to the page of FIG. 21, out of the emission of the light emitting element 54, is picked out by the polarizer 53, and is transmitted through the liquid crystal element 51 at an ON state and reaches the polarizer 52. Since the linearly polarized light then fails to coincide with the polarization direction of the polarizer 52, it is absorbed by the polarizer 52, and as a result, this area is externally recognized as "black."
In this way, to present information using the emission of the light emitting element 54, numbers and the like in black, indicating time and other information, are presented on the background of the emission color of the light emitting element 54.
As shown in FIG. 21, the light emitting element conventionally emits a monochromatic light in the watch of the type that presents information using the light emitted by the light emitting element disposed beneath the polarizer. The background color is thus monochromatic, for example, white only when the background color is presented by the emission color as represented by the arrow C in FIG. 21. Although the mode of display works in a simple presentation of the numeric information and the like, the mode of display may not be sufficient in the job of calling a viewer's attention.
FIG. 10 shows a major portion of an embodiment of a conventional electronic watch, particularly of a display element of the electronic watch. The electronic watch of this embodiment comprises the liquid crystal element 8, a first polarizer 11 arranged on one side of the liquid crystal element 8, a second polarizer 15 opposed to the first polarizer 11 with the liquid crystal element 8 interposed therebetween, and the back light 28.
The conventional watch includes the second polarizer 15, which is an ordinary polarizer like the first polarizer 11, and is arranged between the liquid crystal element 8 and the back light 28. This embodiment is also different from the embodiment shown in FIG. 21 in that the back light 28 of this embodiment emits lights of different colors in a plurality of areas while the conventional back light 54 emits a monochrome light from its entire surface.
The mode of display shown in FIG. 10, namely, the travel of the natural ambient light and of the emission of the back light 28, remains unchanged from that shown in FIG. 21. When the natural ambient light is used, the background is presented by irregularly reflected light from the back light 28 as represented by an arrow P, and the numeric information and the like are presented in black as represented by an arrow Q. When the emission of the back light 28 is used, the background is presented in the emission color of the back light 28 as represented by an arrow C, and the numeric information and the like are presented in "black" as represented by an arrow D.
In this watch, the back light 28 is provided with a plurality of emission areas S1, S2 and S3, and colors externally recognized may be emission colors of areas S1, S2 and S3 in the optical state represented by the arrow C. More specifically, the background colors with the back light 28 lit may be separately presented in yellowish green, red and orange or other colors may be used. The mode of display in which the background color on the display screen is switched between a white and another particular color such as yellowish green depending on whether the back light 28 is lit or extinguished is novel and appealing to the viewer.
As understood from the above discussion, numeric numbers and the like are simply presented in "black" in the conventional electronic watch both when the natural light is used and when the emission of the light emitting element is used, and the mode of display for numeric information and the like is simple.